I. Field of the Invention
The present invention relates to tools for sanding or grinding. More particularly, the present invention relates to a contour sanding apparatus for use with hand-held power tools, enabling a user to abrade contoured surfaces.
II. Description of Related Art
Belt sanders have been used for abrading or sanding many different types of surfaces. Free standing or bench mounted belt sanders typically have three rollers, which control the travel of the abrading belt. One of these three rollers will be driven and the other two rollers remain idle or free spinning. Normally the work area of these belt sanders is in between the two idler rollers.
Most of today""s bench top or pedestal type belt sanders will incorporate a rigid planar work plate that is secured and located within this work area. The abrading loop or belt will travel in front of the work plate, which is used as a support on the backside of the sanding belt while abrading the workpiece on the front side of the sanding belt. As the work plate is a rigid planar plate, these belt sanders are adapted primarily for abrading flat or straight surfaces and, consequently, cannot effectively sand contoured surfaces.
Power sanders having contouring capability are currently available. However, these are more costly and are generally limited to use on a specific contour. Accordingly, some of today""s contour abrading is still being done by means of time consuming and tiresome efforts of physically sanding by hand.
A number of patents are directed to power sanding of contours. For example, U.S. Pat. No. 6,116,999, discloses a sander with the capability of sanding a bullnose concave surface by using sheets of abrasive materials, clamped in accordance with a flexible pad. Through capable of abrading a concave workpiece, it is limited to only that concave surface.
U.S. Pat. No. 5,725,423, discloses a back-up pad provided for supporting an abrasive article during abrading. Though capable of abrading some contours, this method is limited to abrading only slights contours.
U.S. Pat. No. 5,662,519, discloses a contour sander designed for sanding the details and curves of automobile body panels. This sander is limited to manual use and may not be adapted for use on a power sander.
U.S. Pat. No. 5,700,187, discloses a flexible device for holding abrasive materials, which can be adjusted to a variety of shapes. Though capable of conforming to a variety of curved shapes, the device has to be manually adjusted to each shape separately.
U.S. Pat. No. 3,956,858, discloses a flexible hand held abrading tool, which can easily conform to curves and contours. However, this is also limited to a manually operated hand held tool and not for use on power sanders.
In addition to traditional belt sanders, a number of hand held attachments directed at sanding and grinding have been introduced to the market. Typically, these attachments are mechanically coupled to the power tool at the site where a standard attachment, such as a drill-bit or sanding-wheel is otherwise placed. In spite of the advantages that these add-on devices may provide, they have not adequately addressed the problems associated with grinding or sanding surfaces intended to be non-flat. This is because these existing devices present either a flat or fixed-radius surface as a backing for the grind/sanding belt, which is a serious limitation for ornate work pieces incorporating curved portions. As a consequence, portions of such complex and ornate work-pieces tend to be either over-worked or under-worked during the finishing process.
A number of patents have been directed to hand held sanding attachments. For example, U.S. Pat. No. 4,551,951, discloses a detachable portable continuous-belt driving head for use in conjunction with an air driven rotatable spindle. By wrapping a sanding belt around the work-piece, this device can be used to sand or grind a significant portion of the circular contour of a cylindrical work-piece such as a pipe. However, wrapping such a belt around an uninterrupted span of pipe requires that the belt be xe2x80x98seamed,xe2x80x99 that is that it has seam where it can be opened and then rejoined. In other words, before this device can be used on a pipe, the ends of the grinding belt must be separated at the seam, the belt must be wrapped around the pipe, and the ends o the belt must be rejoined. This process is time consuming. Furthermore, the use of seam-containing grinding belts can be hazardous, since they are vulnerable to operator error in connecting and disconnecting the belt that can lead to the belt flying off the rollers, causing injury or damage.
U.S. Pat. Nos. 4,858,390 and 5,031,362, disclose similar endless-belt grinding attachments for use in conjunction with typical hand-held electric or pneumatic power drills. Both of these devices have a drive pulley, driven by the output of a power tool, and in idler-pulley disposed at the end, distal to the drive pulley, of an arm member. In use, a grinding belt is mounted on these pulleys. Because the grinding belt so mounted conforms to a single longitudinal axis these devices are limited to relatively small angles of contact when used with work pieces having curved contours, such as pipes or toroidal shapes. Consequently, it is difficult to use either of these devices to satisfactorily grind such curved surfaces.
U.S. Pat. No. 4,578,906 discloses another device using an endless grinding belt. This device is similar to those of U.S. Pat. Nos. 4,858,390 and 5,031,362 in that it has two pulleys, one being a drive-pulley. These pulleys are mounted at the ends of a longitudinal arm-member. An endless grinding belt fits over the pulleys and is stretched to an essentially flat configuration, so that it presents a flat grinding surface to the work piece. A spring is mounted coaxially with the arm-member and is used as a bias means for keeping the belt under tension and thus flat. However, this device has the same limitations as those described above.
Therefore, there is a need for a contour sanding device for use with standard sanding belts, which can work the surface of a variety of complex, ornate shapes, and can provide proper backing for a variety of contours or flat surfaces of a work-piece.
The present invention is a contour sanding apparatus for driving a sanding belt. For purposes of this application, the term sanding belt means an abrasive belt, such as those manufactured of sandpaper, steel wool, SCOTCHBRITEO(copyright), or any other art recognized abrasive belts.
In one embodiment of the invention, the apparatus includes a body and a drive pulley rotatably attached to the body, the drive pulley comprising a drive-axle dimensioned for attachment to a source of rotation. A primary arm is fixedly attached to the body and includes an end portion to which a primary idler pulley is rotatably attached. A secondary arm is also provided. The secondary arm includes tensioning means for maintaining the sanding belt in tension, and a first end portion to which a secondary idler pulley is rotatably attached. The secondary idler pulley is disposed in relation to the primary idler pulley such that the sanding belt forms a sanding portion between the primary idler pulley and the secondary idler pulley. The sanding belt is dimensioned for disposal about the drive pulley, the primary idler pulley, and the secondary idler pulley such that the a sanding portion of the sanding belt, disposed between the primary idler pulley and the secondary idler pulley, may be made to conform to a plurality of contours.
In the preferred embodiment of the invention, the secondary arm extends from, and is pivotally attached to, the primary arm via a second end portion, which is disposed within a central slot in the central portion of the primary arm. The preferred secondary arm includes a non-slidable section that includes the second end portion, and a slidable section that includes the secondary idler pulley. It is preferred that a sleeve be slidably disposed about the non-slidable section such that the sleeve and the slidable section may slide along the non-slidable section when acted upon by the axial force exerted by the tensioning means. The preferred tensioning means is a spring disposed between the slidable section and the non-slidable section such that the spring exerts a axial force upon the slidable section relative to the non-slidable section.
In some alternative embodiments of the invention, the tensioning means is a fluid cylinder having a non-slidable section that includes the second end portion, and a slidable section that includes the secondary idler pulley. In these embodiments, the fluid cylinder includes a connection for pressurizing fluid within the fluid cylinder such that an axial force is exerted upon the slidable section relative to the non-slidable section. In other embodiments, the sleeve is eliminated and the slidable portion is dimensioned to slide along the non-slidable portion. In still other embodiments of the invention, the tensioning means of the secondary arm is eliminated and the tension on the sanding belt is adjusted by adjusting the location of the drive pulley for a desired profile or by utilizing an elastic sanding belt, such as to described in pending U.S. Application No. 19/519,086, filed by the present inventors on Mar. 6, 2000, which is incorporated herein by reference.
The preferred embodiment also includes a retainment-arm to which a retainment-pulley is mounted. The preferred retainment-arm is pivotally connected to the primary arm and disposed such that the retainment pulley contacts the sanding belt and directs it through a channel in the body. In some embodiments of the invention, one or more additional retainment pulleys are disposed at other locations about the apparatus to further guide the sanding belt. In still others, the retainment pulley is eliminated. In these embodiments, the body is either eliminated or is dimensioned to avoid contact with the rotating sanding belt.
The preferred retainment-arm, primary idler pulley, secondary idler pulley and drive pulley all include a drive layer manufactured of a flexible and substantially resilient material, such as rubber. This resilient material is preferred as it counteracts variations in belt tension and allows non-standard sanding belts, such as belts made of a material of the type sold by the Minnesota Mining and Manufacturing Company of St. Paul, Minn. under the trademark SCOTCHBRITE(copyright).
The preferred embodiment of the invention also includes support attachments that may be disposed between the primary arm and secondary arm to provide support to the sanding portion of the sanding belt when contoured surfaces are sanded. In one preferred embodiment, the apparatus is sold in kit form along with a variety of support attachments; preferably including at least one flex plate attachment and at least one support shelf. In such an embodiments, a wider range of contours may be sanded than is possible by utilizing the apparatus alone.
The preferred flex plate attachment is disposed between, and attached to, the primary arm and the secondary arm proximate to the primary idler pulley and the secondary idler pulley. The flex plate attachment includes a lower support area, an upper support area, and a flexible work area that extends between the lower support area and the upper support area. The length of the flexible work area may be varied to allow plurality of arcs to be formed, with short work areas allowing the user to sand small diameter profiles and long work areas allowing large diameter profiles to be sanded. Accordingly, it is preferred that the kit includes flex plate attachments having flexible work areas of varying lengths.
The flex plate attachment may be manufactured of any material that is flexible enough to form a plurality of arcs without breaking or plastically deforming. The preferred materials for the flex plate attachment are polycarbonate and spring steel, which are preferred for light duty and heavy duty applications respectively. However, hard rubber or other spring metals are utilized in other embodiments. In some embodiments, the flex plate attachment is coated with a wear resistant coating, such a polytetraflouroethene.
The preferred support shelf is substantially rigid and includes a rigid work area that is dimensioned to allow the sanding belt to conform to a desired contour. The preferred rigid work area is substantially planar and is utilized to provide support during the sanding of flat surfaces. However, it is recognized that a variety of rigid work areas, such as concave and convex surfaces, may be formed into the support shelf, allowing the apparatus to sand a particular contour.
In the preferred embodiment, a support attachment is attached to the primary arm and secondary arm via a pair of mounting details, with the lower mounting detail being attached to the primary arm and the upper mounting detail being attached to the secondary arm. A variety of mounting details may be utilized, although the preferred embodiment includes one pivotal snapping detail and one pivotal pinning detail. These details are preferred as they allow the support attachment to be retained upon one of the arms when it is disengaged, allowing the user to avoid removal of the attachment when no support attachment is desired, while allowing for a quick engagement when such an attachment is desired.
The preferred embodiment also includes a locking means for securing the secondary arm in-a desired position relative to the primary arm. Such a locking means allows distance between the arms, and hence the length of the sanding portion of the sanding belt, to be varied. In embodiments utilizing a flex plate attachment, the locking means may be utilized to lock the flex plate attachment into place once it has been flexed to a desired profile.
In the preferred embodiment, the source of rotation for the contour sanding attachment is a separate tool, such as a hand held drill, grinder or the like. In these embodiments, it is understood that the contour sanding apparatus will be sold as an attachment for use with an existing source of rotation and, therefore, will utilize drive axles dimensioned for attachment thereto. Some embodiments of the axles include a smooth or knurled shaft that is dimensioned for gripping by a chuck of a drill or roto-tool. Others, such as those adapted for attachment to grinders, include counter-threaded screw type attachments. In some alternative embodiments, the contour sanding apparatus includes an integral source of rotation. In such embodiments, the drive axle of the drive pulley may be formed integral to the source of rotation, rather than being attached to it.
Therefore, it is an aspect of the invention to provide a contour sanding apparatus that may be adapted for use as an attachment to existing belt sanders and hand held power tools, or as a stand alone apparatus including a source of rotation.
It is a further aspect of the invention to provide a contour sanding apparatus that may include a plurality of support attachments to support the sanding belt so as to follow a desired contour.
It is a further aspect of the invention to provide a contour sanding apparatus that will allow the sander to abrade a variety of contoured surfaces.
It is a further aspect of the invention to provide a contour sanding apparatus that will be safe, easy to use and affordable for consumers.
It is a further aspect of the invention to provide a contour sanding apparatus that may include a flex plate attachment that enables it to sand either flat or contoured surfaces.
It is a further aspect of the invention to provide a contour sanding attachment that may be utilized with a polishing sanding belt, such as a SCOTCHBRITE(copyright) belt.
It is a further aspect of the invention to provide a contour sanding attachment that may be utilized with an elastic sanding belt.
It is a still further aspect of the invention to provide a flex plate attachment for a contour sanding apparatus that aids in the sanding of a variety of contours.
These aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims and accompanying drawings.